Clinical, Radiographic, and Histologic Evaluation of Regional Odontodysplasia: a Case Report with 5-year Follow-up.

Regional odontodysplasia is a developmental anomaly that affects the primary and permanent dentitions. This disorder is generally localized in only one arch and its etiology is still unknown. Clinically, the affected teeth have an abnormal morphology and are typically discolored. Radiographically, these teeth show a ghost-like appearance. This paper reported the results of radiographic, histologic and laboratory findings about the case of a 5-year-old girl presenting this rare anomaly. Her familial history was negative for any genetic anomaly, regional odontodysplasia or other dental anomalies. The patient's general health was good and no congenital or acquired disease was reported. She was kept under follow-up care until she reached the age of 10 years. Panoramic radiograph showed the involvement of permanent teeth on the right maxillary quadrant. The affected edentulous quadrant was rehabilitated with temporary acrylic maxillary partial denture. The presentation of this case would hopefully have valuable information for pediatric dentists to review the clinical and radiographic features of regional odontodysplasia, yet expediting the diagnosis and treatment of patients with this condition.


Introduction
Regional odontodysplasia (RO) is a rare developmental dental anomaly affecting both the primary and permanent teeth. [1] The prevalence of this condition is not definitely clear since the studies have been mainly based on the case reports. [2][3][4][5] Its prevalence is reported to be less than 1/1000000 and only about 140 cases have been reported in the literature up to the time of this study. [2] It is also known by other terms such as odontogenic dysplasia, ghost teeth, unilateral dental malformation, localized arrest tooth development, familial amelodentinal dysplasia, and odontogenesis imperfecta. This condition affects the tooth structures that originate from the ectoderm and mesoderm. Hitchin described this condition for the first time in 1934. [6] However, the first report that dealt only with the radiographic manifestations of the anomaly was presented by McCall and Wald in 1974. [7] The term odontodysplasia was used by Zegarelli et al. in 1963. [8] Since only one quadrant of the jaw is affected by this condition; regional odontodysplasia was selected as the most acceptable term to describe the condition. [1] This condition mostly involves one quadrant and affects the maxilla twice as frequently as the mandible, [9] with the left maxillary quadrant being the most frequently affected quadrant.
[10] It has a predilection for the central and lateral incisors, with higher prevalence in females compared to males. [1] The etiology of this dental anomaly is unknown.
However, various factors have been proposed as the etiologic agents including local trauma or infection, teratogenic medications, local disturbances of the blood supply, Rh incompatibility, radiotherapy, neurologic traumas, fever, metabolic and nutritional disorders, and vitamin deficiencies. [10] Heredity seems to play no role in the etiology of this condition because no familial case of such condition has been reported. [11][12][13] Nonetheless, this condition has been reported in association with some medical conditions such as vascular nevus, hemangiomas, epidermal nevus syndrome, orbital coloboma, facial hypoplasia on the affected side, hypophosphatasia, ectodermal dysplasia, and hydrocephalus. [14][15][16][17][18][19][20][21] The diagnosis of regional odontodysplasia depends on clinical and radiographic findings. [22] Clinically, the teeth affected with regional odontodysplasia have an abnormal shape and an irregular super facial contour, with super facial pits and grooves. The teeth are yellow or yellowish-brown in color and appear to be hypoplastic or hypocalcified. The enamel of such teeth is soft when examined with a dental explorer. [23] These teeth are more susceptible to dental caries, very fragile, and they may fracture by minor traumas. [2] Tooth eruption is delayed and teeth might not even erupt at all. After eruption of the teeth affected with regional odontodysplasia, the most common clinical manifestations are periapical infections and abscess formation even in the absence of dental caries. [2,22] Radiologically, the affected teeth illustrate abnormal morphology and hypoplastic crown. Additionally, lack of contrast between the enamel and dentin is usually apparent. The enamel and dentin are very thin, displaying a ghost-like appearance. [2,24] The enlarged pulp chambers, short roots, open apices, and shell-like crowns are the other pathognomonic radiological characteristics. [2,14] This report presents a case of regional odontodysplasia that had affected the right quadrant of maxilla in a 5-year-old girl.   Based on clinical and radiographic findings, the problem was diagnosed as regional odontodysplasia.

Case Report
With both patient's and her parents' consent, the primary teeth on the maxillary right quadrant were extracted due to the pain and infection during a period of 6 months. A temporary acrylic resin prosthetic appliance with a bite plane was fabricated to preserve the alveolar ridge during the period of skeletal growth (Figure 3).  Having obtained the patient's and parents' consent, the maxillary right lateral incisor was extracted due to severe pain and fistula. The surgically-removed tooth was histologically examined under an optical microscope in the ground and decalcified section. In most areas, dentin was atubular with many areas of amorphous material ( Figure 5). Based on the histopathology-cal features, the provisional diagnosis of regional odontodysplasia was confirmed.

Figure 5:
The dentin was atubular in most of the areas with many areas of amorphous material (H & E 400x).

Discussion
Regional odontodysplasia is a rare developmental anomaly. [1][2][3][4] Its exact etiology is uncertain, although several factors are involved. [1][2][3]25] In many cases, RO is probably misdiagnosed as malformed teeth or odontomas. [26] It occurs in both primary and permanent dentitions, with a marked preference for the maxilla. [27] In the present study, similar to the most previous studies, odontodysplasia affected a maxillary quadrant in a female. Although involving the left side of the maxilla is more common, in this report, the right side of the maxilla was affected. Other conditions such as dentinal dysplasia, shell teeth, hypophosphatasia, dentinogenesis imperfecta, or amelogenesis imperfecta can mimic some features of this anomaly. However, these abnormalities tend to affect the entire dentition. [28]  moreover, the lesion might be detected in association with hemangioma. [2][3][4][32][33][34] In this case report, the patient's familial history showed neither any congenital or acquired diseases nor was any known factor found.
The only findings in this case were the patient's belownormal weight and her parental consanguinity, which may be related to her disorder. Several factors including the patient's age, disorder severity, characteristics of the tion may be considered in odontodysplasia treatment. On the contrary, in older children, the abscessed permanent teeth should be extracted with others must be retained until final rehabilitation with implants or fixed prosthesis. [37] The patient was placed on periodic recall to monitor the growth and development of her dental arches. Unfortunately in the present case, the patient was referred to the Department of Pediatric Dentistry after the involvement of dental pulp, so the prophylactic treatment was not possible. Therefore, pulp therapy was indicated in this situation. Early diagnosis and clinical and radiographic characteristics of these patients are of great importance. If the patient had been referred to the department sooner, prophylactic treatment could have been considered and her teeth would probably have been saved and consequently, the development of alveolar ridge has been expedited.

Conclusion
Treatment of a child with regional odontodysplasia requires a multidisciplinary approach. Consultations be-tween pediatric, prosthodontic, and orthodontic specialists are necessary to provide the best treatment plan.
Treatment planning should be designed separately for each individual case. It depends on many factors such as the patient's age, medical history, involvement extension, teeth eruption, esthetics, and the development stage of pathology. The presentation of this case adds valuable information for pediatric dentists to review the clinical, radiographic and histological features of RO.
Moreover, it would remind them that early referral of these patients would be of great importance for their early treatments.